Countersink attachment for bits.



COUNTERSINK ATTACHMENT FOR BITS.

Specification of Letters Patent.

Patented Sept. 9, 1913.

Application filed August 1, 1910. Serial No. 575,005.

To all *wh0mit may concern:

Be it known that I, JOHN WI-IY'IE, a citizen of the United States,residing at Everett, State of Washington, have invented a new and usefulImprovement in Counter- The object of my invention is, in general,

to improve and simplify such devices, and

in particular to provide a device of this character which will do smoothwork without roughening or breaking the wood, and one also which willhave sufficient resistance by the time it has made the desired depth ofcountersink, that it will overhaul the bit, that is, free the screwwhich serves to draw the bit into the wood.

In the drawings I have shown my invention in the form which is nowpreferred by me.

Figure 1 is an elevation or side view of my device. Fig. is an end viewof the cutting end of the form of my device shown in Fig. 1. Figs. 3 and4c are like views of my device having a modified form of cutting teeth.

In the countersunk attachments which have heretofore been generallyemployed,

one of the most serious objections is their tendency to roughen thesurface of the board outside of the countersunk area. Another principalobjection is that they will not, with certainty, free the bit from itsin-drawing tendency, and, therefore, the bit and its attachedcountersink will keep on boring into the wood, and the countersunk areawill often be made larger or deeper than is intended or desired. Theresult is invariably, countersinks of varying size and depth.

The common countersinks quite generally have their teeth so shaped thatthey are very small or almost reduced to nothing at the margin of thecentral bore which receives the bit.

It is one of my objects to so shape the teeth that they will have apronounced tooth shape at this inner margin, whereby they will cleanlyout the borings produced by the bit as well as cut the wood within thearea of the countersink; this shape is clearly shown in Figs. 1 and 3.In these two figures no attempt has been made to show the outline of anyteeth which lie in the rearmost half of the device, for to do so wouldcomplicate the drawing. thus be considered as being an elevation of theouter side of one half of the device, the plane of out being a centrallongitudinal one.

The device consists of a tubular body adapted to fit over a bit providedwith cutting teeth upon one end which is beveled and forms thecountersink. It is also provided with a set screw or other convenientmeans for securing it in place upon the bit,

The cylindrical body 1 has a central bore 10 of such size as, to fitover a bit of the size with which it is intended to use it. The lower orcutting end is beveled to form a cone having the same angle as thatdesired for the sides of the countersink. "in this conical end areformed the cutting teeth, these extending with their akes substantiallyparallel with the outer surf-aces of the cone. The outline shape ofthese teeth may be varied somewhat. have found that the best results areobtained when their depth is relatively considerable, and also preferThese figures may that their surfaces beat unequal angles for one side,'31, which is the advancing side of the teeth, at rather a sharp angle,approach- Ling a perpendicular to the plane, of reV.0l1ition. {Theopposite side -30 is at a much flatter angle. This form makes of eachtooth a chisel which will smoothly and cleanly out the wood, avoidingsplintering or breaking out of particles extending byond the margin ofthe countersink.

I prefer that the straight sides of the body 1 be provided with channels2 in line with the channels 3 in the conical end. These I have hereinshown as having their sides at equal angles. Above the grooved orchanneled sides I bore and thread the wall and insert a set screw 5, bywhich the device may be secured in place upon a bit.

In Figs. 3 and 4; I have shown a modified form of construction, themodification consisting in making the toothed end with two differentslopes or cones, a cone 6 of sharper angle being interposed between theterminal cone and the cylindrical portion 1. This ingrooves 2. Thismodification is of value where it is desired to countersink to suchdepth that the head of the screw will be suf ficiently beneath thesurface to perihit the insertion of a wooden plug, thereby the screwhead. The upper cone 6 fornis a smooth walled recess of truly 1otat1vesurface, for which plugs may be made which tion above, being thecylindrical body section of Fig. 1 and the cone fru st1im 6 pf Fig. 3,the bottom of the channels 8 in the tip section extend upward into one;face of the section above, as is clearly seen in Figs. 1 and 3. Theunder side of the face thus formed at the lower end of the upper groovecreates a, stop which, byimpeding the free escape of the cuttings,prevents further entrance of the bit or countersink into the wood.

I have found that a countersink having the form of teeth shown will outfreely until it reaches a certain depth corresponding to that desiredfor the countersink, and will by this time pro1duce'a resistance orbackward pull upon the bit sufficient to relieve or free the indrawingscrew of the bit from its hold upon the wood, ,thus stopping the advanceof the bit into the wood. It thus acts, a stop to limit the depth of thehole made by the bit.

What I claim as my invention is 1. Acount ei-sink for wood havinga,coned 77 end provided with teeth having their advancing face at arelatively greater1'angle to the face of the countersink than theirother face; the section of the countersink next above said coned endbeing toothed with the "outer points of the teeth matching 'w 'i'th thepoints of the cutting teeth of the coiie'cl end, the two faces of theseupper teeth 'beingof,substantially like angle, the bottom angles of theteeth upon said coned end eX- tending into one face of the teeth aboveto form a shoulder. A v

ou ntersinl a r its cutc'el1edjand provided with teeth disposed. in two:Sec'ti01ll those in the section 11l3t-,tl1 n(l h ihg z rh'1a with theiror cutting face maki ng a relatively sharp angle with the surface thecountersink the teeth. upon the section adjoining having their a vancingface at a relatively flatter: angle with the surface "of thecountersink, eurfa'ces of the teeth in both sec-' tions continuing asplanes to intersections forming shoulders. I v 3 countersink attachmentfor bits havii1g its formed as two frustuins of cones, the end frustun1having a greater angle with the axis than the section therefrom, bot-hsections bei1 1g provided with teeth having coincident outer edges, theteeth upon the end frustu n having their advancing face at a relativelyshar per v a than those upon th e inner fru s tuin-,a1i with the innerend of this face extending into a side of a tooth of the section above.

v JOHN WHYIE. Witnesses S .1I ER D D. MIDISEKE.

